1. Field of the Invention
The present invention relates generally to inkjet printing systems and more particularly to an apparatus and method for cleaning inkjet printing systems.
2. Description of the Background of the Invention
Inkjet printing systems include one or more inkjet printheads, each inkjet printhead including an inkjet nozzle array. Inkjet printing systems are used extensively for high volume printing applications requiring high speed and precision. Dried ink, dust, paper fibers, and other debris can collect on the printhead surfaces, clogging inkjet nozzles and preventing proper ejection of ink therefrom. Therefore, keeping the inkjet nozzles free of ink and debris is crucial to the efficient operation of such systems.
Inkjet printheads are cleaned using a variety of methods including scraping, vacuuming, flushing with a fluid, or other methods. In one such cleaning system, ink droplets, dust, and debris are scraped off a printhead surface by an edge portion of a cleaning blade that contacts the surface. Another such cleaning system has a vacuum orifice that is positioned over a printhead nozzle array and an area of the printhead surface around the nozzle array. A gap between the vacuum orifice and the printhead surface provides sufficient space for the passage of documents yet enables the vacuum to clean both the printhead surface and the printhead nozzle array. Yet another cleaning system utilizes a stream of air angled toward a surface of a document moving under a printhead. The stream of air is directed toward the printhead, thereby preventing dust particles entrained in air near the document surface from collecting on the printhead.
One of the other methods for cleaning an inkjet printhead includes an ultrasonic liquid wiper. A cleaning nozzle is confrontingly aligned across a small space from a printhead nozzle array and a meniscus of cleaning solution is allowed to bulge out of the cleaning nozzle to make contact with the printhead nozzle array surface. The cleaning solution is then ultrasonically excited by a piezoelectric material, thereby providing a high frequency liquid wiper to clean the printhead nozzle array. A vacuum nozzle then removes the cleaning solution and any ink dissolved therein.
Still other printhead cleaning systems include an adsorbent material such as a thread that is movably positioned across a printhead surface proximate to a printhead nozzle array. Dust and other debris are caught on the thread instead of collecting on the printhead surface. A continuous supply of clean thread from a spool allows dust and debris to be continuously captured.
Some printhead cleaning systems utilize both scraping and vacuum. One such system has a suction unit capable of applying suction to several nozzles of a nozzle array, and that also translates across a face of a printhead. The suction unit includes a resilient blade on a side of the unit in the direction of motion allowing the unit to scrape the surface of the printhead and also apply suction to the nozzles across an entire printhead surface.
Other printhead cleaning systems include a nozzle array plate positioned between a printhead nozzle array and a moving paper web. The plate has a narrow slit proximate to the printhead nozzle array allowing ink to be sprayed through the plate onto the paper web. To prevent ink mist from contaminating the printhead nozzle array surface, a fluid is flushed across the surface in a small gap between the plate and the surface. The fluid is introduced above the printhead nozzle array, flows downwardly over the nozzle array and then is vacuumed by a suction opening below the narrow slit.
Another printhead cleaning system includes a translating solvent delivering wiper and vacuum cleaning block. The cleaning block has a solvent delivering passageway on a side of the unit in the direction of motion that delivers solvent to the printhead surface proximate to an edge of a blade portion that makes scraping contact with the printhead surface. A vacuum canopy opposite the blade portion vacuums the solvent and debris loosened by the blade portion. In addition, a vacuum hood capable of sealingly engaging the printhead surface is positioned on a side of the unit opposite the direction of motion. The vacuum hood vacuums particulate matter from the printhead surface and from within nozzles of the printhead nozzle array.
Yet another printhead cleaning system dribbles small ink droplets out of nozzles. Strands of material capable of attracting and absorbing ink mist, such as ordinary string, are positioned in contact with or adjacent to the printhead surface and proximate to the nozzles. The dribbled ink droplets keep the nozzles clear of ink, and are absorbed and carried away on the strands of string.